Untethered, unmanned mobile systems are increasingly employed for missions on land, sea and in the air. Current unmanned systems typically employ Radio Frequency (RF) communications for system management and mission operations. Unmanned systems sometimes include on-platform photovoltaic (PV) cells which convert incident solar energy to electrical energy which is then used to power platform, or payload, operations. They may also include optical systems for imaging, mapping or other sensing functions. Additionally, free space optical (FSO) communication links to and/or from the platforms have been demonstrated in a few instances. FSO directional communication links can operate with lower latency, higher bandwidth and longer range than conventional RF links and are an area of increasing interest in the unmanned system community. Any optical device such those mentioned above which makes use of optical energy that is provided to it will be referred to herein as an optical receiving device.
In regard to optimizing the performance of on-platform optical receiving devices it is desirable to optimize the characteristics (e.g. the optical intensity) of incoming light which passes through the surface of the device. A significant, and frequently detrimental, effect can be the diminution of signal intensity because of reflection losses at the interface of the device. This can be due to the refractive index mismatch between the device and its surroundings, surface structure, or other effects. Antireflective (AR) technology is frequently used to minimize such interface reflection losses. AR implementation typically involves the engineering of coating layers, and/or surface structures which can be applied to individual, or multiple, optical receiving devices.